Centrifuge

ABSTRACT

A centrifuge which comprises a rotary centrifuge shaft, a cylindrical drum arranged about said shaft and having end walls, the centrifuge shaft being provided with two pairs of channels which create communication between the interior of the centrifuge and inlet and outlet conduits at the two ends of the centrifuge shaft. One pair of channels open into the interior of the centrifuge at one end thereof and are spaced from one another, while the other pair of channels open in a corresponding manner into the interior of the centrifuge at the other end thereof. A disc of a diameter smaller than that of the centrifuge drum is provided in the centrifuge and fixed to the shaft thereof. The disc is disposed at one end of the centrifuge between the two channels which open at this end. A piston movable along the centrifuge shaft and having substantially the same diameter as the centrifuge drum is arranged between the disc and the other end of the centrifuge. In another embodiment, the centrifuge has two stationary discs which are disposed each at one end of the centrifuge and between the mouths of the respective pairs of channels. In this embodiment, the movable piston is displaceable between the two stationary discs.

United States Patent [191 Uden [ Oct. 7, 1975 [54] CENTRIFUGE [75] Inventor: Bengt Udn, Raa, Sweden [73] Assignee: AS Pellerin/Zenith, l-lelsingborg,

Sweden 22 Filed: Feb. 12, 1974 21 Appl. No.: 441,866

Primary ExaminerGeorge H. Krizmanich Attorney, Agent, or Firm-Blair & Brown [57] ABSTRACT A centrifuge which comprises a rotary centrifuge shaft, a cylindrical drum arranged about said shaft and having end walls, the centrifuge shaft being provided with two pairs of channels which create communication betweenthe interior of the centrifuge and inlet and outlet conduits at the two ends of the centrifuge shaft. One pair of channels open into the interior of the centrifuge at one end thereof and are spaced from one another, while the other pair of channels open in a corresponding manner into the interior of the centrifuge at the other end thereof. A disc of a diameter smaller than that of the centrifuge drum is provided in the centrifuge and fixed to the shaft thereof. The disc is disposed at one end of the centrifuge between the two channels which open at this end. A piston movable along the centrifuge shaft and having substantially the same diameter as the centrifuge drum is arranged between the disc and the other end of the centrifuge. In another embodiment, the centrifuge has two stationary discs which are disposed each at one end of the centrifuge and between the mouths of the respective pairs of channels. In this embodiment, the movable piston is displaceable between the two stationary discs.

6 Claims, 10 Drawing Figures US. Patent Oct. 7,1975 Sheet 1 of 3,910,489

US. Patent Oct. 7,1975 Sheet 2 of3 3,910,489

US. Patent Oct. 7,1975 Sheet 3 on 3,910,489

CENTRIFUGE This invention relates to a centrifuge and particularly to a centrifuge which is adapted, once fats have been treated with phosphoric acid, to separate the precipitated phosphatides.

Most fats among them fatty oils utilized in the manufacture of foodstuffs, such as margarine, contain in the state they have been recovered from the vegetable or animal feedstock a great or small amount of free fatty acids which are removed by refining with alkali, usually in the form of wet refining which comprises treating the fat with an aqueous solution of alkali, such as soda lye. Refining with alkali is preceded by a treatment of the fat or oil with phosphoric acid for the precipitation of so-called phosphatides. The phosphatides precipitated are separated from the oil prior to the alkali treatment, for instance by centrifugation. The centrifuges as hitherto used often do not continuously discharge the phosphatide sludge separated, and have to be stopped from time to time for discharge of the phosphatide sludge which has been separated, in the centrifuge, from the oil. Depending upon the phosphatide content of the fat it is necessary to perform such a discharge one or two times per shift.

The present invention has for its object to provide a centrifuge with facilities for a continuous discharge of the phosphatide sludge separated from the oil, so that the centrifuge can operate continuously without making it necessary to stop the centrifuge for discharging the phosphatide sludge.

According to the invention, the centrifuge is provided to this end with means which during operation of the centrifuge are adapted to supply a mixture of fat or oil and precipitated phosphatides (hereinafter designated sludge) and to draw off pure oil as well as to draw off sludge separated from the oil.

According to the invention, the centrifuge in its general embodiment comprises a centrifuge shaft supported by bearings at its opposed ends and driven by a motor, a cylindrical drum having end walls and arranged concentrically around the centrifuge shaft, and channels provided in the centrifuge shaft and establishing communication between the interior of the centrifuge and inlet and outlet conduits at the two ends of the centrifuge shaft, said conduits being adapted to supply untreated feedstock and to dishcarge treated material, respectively. Characteristic of this centrifuge is that the channels comprise two pairs of channels the mouths of which in the interior of the centrifuge are spaced apart longitudinally of the centrifuge shaft, the mouths of one pair of channels lying at one end of the centrifuge and the mouths of the other pair of channels lying at the other end of the centrifuge; and the centrifuge includes at least one stationary disc which is located between the mouths of the one pair of channels and extends at right angles to the centrifuge shaft and has a radius smaller than that of the drum; and a circular piston which is disposed around and at right angles to the centrifuge-shaft and has a radius substantially equal to that of the drum, the piston being movable along the centrifuge shaft from an extreme position at one end of the centrifuge to an extreme position at the other end of the centrifuge.

In applying the invention, it is preferred that the relative distance between the mouths of one pair of channels is at least equal to the combined thickness of a disc and the piston.

In a preferred embodiment of the invention, the centrifuge is provided with one stationary disc as described above. This embodiment is primarily intended for the centrifugation of oils in which the resulting sludge is relatively low viscous. In another preferred embodiment, the centrifuge is provided with two such discs, the piston being movable between them. This embodiment is intended for both oils with low viscous sludge and oils with tough and high viscous sludge, such as sludge from soy bean oil.

The invention will be further explained hereinbelow with reference to the accompanying drawings in which:

FIG. 1 shows an embodiment of the centrifuge according to the invention;

FIGS. 2-5 show different stages of the operation of the centrifuge illustrated in FIG. 1;

FIG. 6 shows another embodiment of the centrifuge according to the invention;

FIGS. 7-10 show different stages of the operation of the centrifuge illustrated in FIG. 6.

In the drawings like details have been designated by the same reference numerals.

The centrifuge illustrated in FIG. 1 comprises a shaft 1 to which a drum 2 having end walls 3 and 4 is fixed. The shaft 1 has two pairs of channels 5, 6 and 7, 8, respectively. The channels 5, 6 are connected at their one ends toinlet or outlet conduits 13, 14, 15 and 16, while the channels open at their other ends into the drum 2 spaced from one another, as viewed in the longitudinal direction of the centrifuge shaft. The channels 7 and 8 are arranged in a like manner as the channels 5, 6 so that, as will appear from FIG. 1, the two pairs of channels 5, 6 and 7, 8, respectively, open each at one end of the drum 2. A disc 9 is fixed to the centrifuge shaft 1 substantially at right angles thereto between the mouth 17, 18 of the channels 5, 6 and the drum 2. The disc 9 has a radius smaller than the radius of the drum 2, so that there is formed between the disc 9, the drum 2 and the end wall 3 an annular passage 21 which is in communication with the channel 5 for discharging material from the centrifuge or supplying material to it. A circular piston 10 is disposed on the centrifuge shaft 1. The piston is shown in position at the other end of the drum between the mouths 19, 20 of the channels 7, 8. Like the disc 9 the piston 10 is arranged substantially at right angles to the centrifuge shaft 1, but as distinct from the disc 9 the piston '10 is movable along the centrifuge shaft 1 and has a radius substantially equal to that of the drum 2. Moreover, the centrifuge is supported in a conventional manner at its opposed ends, as has been indicated at 1 l in FIG. 1, and is adapted to be driven by a motor (not shown).

The function of the centrifuge illustrated in FIG. 1 will now be described with reference to FIGS. 2-5. FIG. 2 shows the centrifuge in continuous operation at the separation of low viscous phosphatide sludge from oil treated with phosphoric acid, while FIGS. 3-5 show how the centrifugeis emptied for instance upon exchange of product type or how it is operated at the separation of tough and highly viscous sludge, such as soy bean oil.

As shown in FIG. 2, the oil and sludge mixture obtained at the treatment with phosphoric acid is supplied to the rotating centrifuge through the channel 6. The oil and the sludge have an approximate density of 0.9

g/cm and 1.5 g/cm, respectively, and a suitable rate of rotation for a centrifuge having a length of about 2 meters and a diameter of about 0.4 meters has proved to be about 1000 rpm. The heavy sludge is separated from the light-weight oil and migrates radially towards the wall of the centrifuge drum 2. From thatwall the sludge then moves laterally, that is in the longitudinal direction of the centrifuge shaft, to the left in FIG. 2 and through the annular gap or passage .21 between the disc 9 and the drum 2 and from there it passes through the channel 5.. The oil which is the more light-weight phase, migrates from the inlet through the channel 6 to the channel 7 while the heavier sludge is separated off. The oil freed from sludge is drawn off through the channel 7.

If the separated sludge is tolerably low viscous the operation as now described may in principle continue without interruption. Even though the sludge separated is low viscous, it is sometimes neccessary, however, to discontinue operation, for instance at inspection, maintenance or shutdown. In such cases the procedure illustrated in FIGS. 3-5 is adopted. It may be said that FIGS. 3-5 combined with FIG. 2 also relate to the case when the separated sludge is tough and, does not by itself move out of the centrifuge, through the gap between the disc 9 and the drum 2,. but is builtup against the drum 2 and has to be positively emptied by means of the piston 10.

When the centrifuge illustrated in FIG. 2 is to be stopped and emptied, the first step is to interrupt the supply of oil/sludge mixture to the channel 6 and to supply water instead through said channel. The water which has a density between that of the. oil and the.

sludge, interposes between them, expelling the-oil contained in the drum through the channel 7. When all oil has been expelled from the drum water is supplied through the channel 8 into the space 22 (FIG. 1) between piston 10 and end wall 4 whereby the piston 10 is caused to move along the centrifuge shaft 1 towards the disc 9. During its movement the piston 10 forces the mixture of sludge andwater out of the drum 2 through the channel 5, as shown in FIG. .4. When the 7 piston 10 has reached itsend position in which it is applied against the disc 9, the supply'of water through the channel 8 is interrupted. I

To put the centrifuge into operation again the piston 10 is moved towards its earlier position betweenthe mouths 19, 20 of the channels 7 and 8 by again supplying oil/sludge mixture. This supply first takes place through the channel *to move the piston to the right in FIG. 5 past the mouth 17 of the channel 6, and

after that the supply'of oil/sludge mixture is switched over to the channel 6. Such a switch-over fromchannel' 5 to channel 6 can be dispensed with by arranging the disc 9 at the mouth 17 of the channel 6 and, in addition, by designing the piston 10 in such a way that in its lefthand end position abutting the disc 9 it does not cover the mouth 17 of the channel 6 but has said channel between itself and the disc 9. During the return of the piston 10 towards its earlier position the centrifuge is with, in which case, however, the oil contained in the drum at the closure of the channel 6 will be discharged together with the sludge throughthe channel 5.

The I embodiment illustrated in FIGS. 6-10 corresponds. to that illustratedin FIGS. 1-5 except for the fact that a further disc 12 has been placed between the mouths 19, 20of the channels 7, S at the other end of the-centrifuge. This embodiment is superior to the embodiment illustrated in FIGS. 1-5 in that it is=also capable of treating oils containing a tough and highly viscous sludge without necessitating: an interruption of the centrifuging operation for the discharge of sludge. The function of the centrifuge shown in FIG.,6 will appear from FIGS. 7-10.

As earlier described in conjunction with the FIG. 1 centrifuge having one disc 9 the oil/sludge mixture: is

supplied, in the operation of the centrifuge having two.

discs 9, 12, through the channel 6 and pure oil is drawn off through the channel 7, while the separated sludge, if it is low viscous, continuously escapes via the channel 5. If the separated sludge is tough, the supply of oil/- sludge mixture is shifted fromthe channel. 6 which is closed, to the. channel 8 in order that the piston 10 be moved to'the left, as viewed in FIG. 8, 'past the mouth 19 of the channel 7. When the piston, 10 has gone past the. mouth 19 of channel 7 the supply of oil/sludge mixture is again shifted and is supplied instead through the channel 7. The centrifuge is constantly rotating and while the piston is moved to the left towards the disc 9 by the pressure from the oil/sludge mixture,-the newly supplied oil/sludge mixture is divided between the piston l0 and the disc 12 into oil and sludge,as shown in FIG. 9, simultaneously as the sludge and the oil between the piston 10 and the disc ,9 is discharged through the channelr5. In order to reach its end position abutting against the disc 9 the'piston 10 finally goes past the mouth 17 of channel 6, as will appear from FIG 10, whereby the centrifuged oil which has been supplied through channel 7, can escape through channel 6. The separated sludge escapes, if it is low viscous, through channel 8 or collects against the drum 2,

if it is tough. As will appear from a study of FIGS. 7 and 10, these are mirror-reversed pictures of each other and in order again to reach the position shown in FIG. 7 it is only necessary to repeat the procedure just demirrorthat described above with the exception, however, that before the channel 6 is closed and the piston 10 is moved to the left, water is supplied through the channel 6 until oil in the drum 2 has been expelled through the channel 7. The mixture then expelled by the piston 10 through the channel 5 will consist of sludge and water instead of oil and water, as shown in FIG.9.

The'ce'ntrifuge according to the invention has been described above with reference to the specific case in which fat treated with phosphoric acid is centrifuged for the separation of precipitated phosphatides, but it will be realized that the centrifuge according to the invention is generally useful for the separation of liquids or suspensions of different densities from each other. The above description made with reference to the accompanying drawing figures thus is not intended to restrict but only to illustrate the invention the scope of which will be apparent from the appended claims.

What I claim and desire to secure by Letters Patent 1. A centrifuge comprising a driven centrifuge shaft supported by bearings at its opposed ends a circular piston movable along the centrifuge shaft, a cylindrical drum having end walls and arranged concentrically around the centrifuge shaft, and channels provided in the centrifuge shaft and establishing communication between the interior of the centrifuge and inlet and oulet conduits at the two ends of the centrifuge shaft, said conduits being adapted to supply untreated feedstock and to discharge treated material, respectively, wherein the channels comprise two pairs of channels the mouths of which in the interior of the centrifuge are spaced apart longitudinally of the centrifuge shaft, the mouths of one pair of channels lying at one end of the centrifuge and the mouths of the other pair of channels lying at the other end of the centrifuge; and the centrifuge includes at least one stationary disc which is located between the mouths of the one pair of channels and extends at right angles to the centrifuge shaft and has a radius smaller than that of the drum; and the circular piston is disposed around at right angles to the centrifuge shaft and has a radius substantially equal to that of the drum, the piston being movable along the centrifuge shaft from an extreme position at one end of the centrifuge to an extreme position at the other end of the centrifuge.

2. A centrifuge as claimed in claim 1, wherein the relative distance between the mouths of a pair of channels is at least equal to the combined thickness of a disc and the piston.

3. A centrifuge as claimed in claim 1, wherein one disc is provided and the piston is movable between the disc and the opposite end wall of the centrifuge.

4. A centrifuge as claimed in claim 1, wherein two discs are provided and the piston is movable between said two discs.

5. A centrifuge as claimed in claim 2, wherein one disc is provided and the piston is movable between the disc and the opposite end wall of the centrifuge.

6. A centrifuge as claimed in claim 2, wherein two discs are provided and the piston is movable between said two discs. 

1. A centrifuge comprising a driven centrifuge shaft supported by bearings at its opposed ends a circular piston movable along the centrifuge shaft, a cylindrical drum having end walls and arranged concentrically around the centrifuge shaft, and channels provided in the centrifuge shaft and establishing communication between the interior of the centrifuge and inlet and oulet conduits at the two ends of the centrifuge shaft, said conduits being adapted to supply untreated feedstock and to discharge treated material, respectively, wherein the channels comprise two pairs of channels the mouths of which in the interior of the centrifuge are spaced apart longitudinally of the centrifuge shaft, the mouths of one pair of channels lying at one end of the centrifuge and the mouths of the other pair of channels lying at the other end of the centrifuge; and the centrifuge includes at least one stationary disc which is located between the mouths of the one pair of channels and extends at right angles to the centrifuge shaft and has a radius smaller than that of the drum; and the circular piston is disposed around at right angles to the centrifuge shaft and has a radius substantially equal to that of the drum, the piston being movable along the centrifuge shaft from an extreme position at one end of the centrifuge to an extreme position at the other end of the centrifuge.
 2. A centrifuge as claimed in claim 1, wherein the relative distance between the mouths of a pair of channels is at least equal to the combined thickness of a disc and the piston.
 3. A centrifuge as claimed in claim 1, wherein one disc is provided and the piston is movable between the disc and the opposite end wall of the centrifuge.
 4. A centrifuge as claimed in claim 1, wherein two discs are provided and the piston is movable between said two discs.
 5. A centrifuge as claimed in claim 2, wherein one disc is provided and the piston is movable between the disc and the opposite end wall of the centrifuge.
 6. A centrifuge as claimed in claim 2, wherein two discs are provided and the piston is movable between said two discs. 